The present invention relates to programming of cycle duration and control functions performed during the service cycle of electrically operated appliances. The invention relates particularly to programming of the duration and function of the service cycle of domestic appliances such as washing machines, clothes dryers and microwave cooking ovens. Such appliances typically employ an electromechanical programmer timer powered by a subfractional horsepower timing motor operating a series of cams for making and breaking a plurality of electrical contacts at the appropriate time during the service cycle. The contacts control current flow in circuits for controlling various electrically operated functions on the appliance in a predetermined program sequence.
For example, it is known to employ an electromechanical programmer timer to control the solenoid operated water inlet valve and drain pump motor of a domestic washing machine and to control the timed energization of a magnetron for microwave cooking. Programmer timers for such applications are known to employ a rotatable drum having a plurality of spaced peripheral cam tracks where the drum is driven by an escapement comprising a ratchet and pawl advance mechanism.
In known programmers of the latter type, the timing motor typically provides periodic stroking of the advance pawl, as for example by a rotating eccentric, driven by a suitable rate reducing gear train which is driven by the timing motor. Such a programmer timer provides for a single rate of advancement of the cam drum and relies upon variation of the lobes on the individual cam tracks to provide the desired sequence for programming electrical control functions as the cam tracks are advanced.
Programmer timers of the aforesaid type usually employ a means for permitting manual rotation of the cam drum to preset the programmer at a desired position in the program cycle for beginning the timing motor powered advance of the cam drum. Thus, the length of the program cycle may be varied by manually setting the cam drum at a preselected fraction of its total arc of rotation.
However, it has been desired in certain appliance applications, as for example microwave cooking devices, to find a way or means of providing a variable sequence of timing for the various control functions during the program cycle, where the difference or variation in the timing sequence is related to the overall length or duration of the program cycle selected. It has been proposed to provide a plurality of program timers for controlling the appliance cycle wherein separate programmer timers would be employed for cycle control dependent upon the type or length of program cycle selected.
This proposal, however, has the distinct disadvantage in increasing the cost of the appliance by virtue of the multiple timing motors and gear trains required for providing the desired degree of sophistication of the appliance program cycle.
Alternatively it is known to provide all electronic timing control of the programmer cycle and operate the various control function circuits by employing solid state electronic power switching. This technique has provided the desirable variation in cycle program and timing but has proved prohibitively costly. Accordingly, it has long been desired to provide a way or means for varying the program sequence timing and cycle duration for an electrical appliance with a simple low cost electro-mechanical programmer timer operated by a single timing motor.